/Engine/Source/Runtime/CoreUObject/Public/UObject/PackageResourceManager.h
If unsupported, functions without LocalOnly in their name that take a PackagePath will behave as if the package does not exist in the repository for unmounted LocalPaths If unsupported, functions with LocalOnly in their name will indicate the lack of support when called with unmounted LocalPaths; see each function's description for its precise behavior
bool SupportsLocalOnlyPaths()